Ahni Huang is an incredibly rich and talented young woman. Her brain has been infiltrated by nanotech, giving her an on-board AI and communications device, and she is a capable empath. She also has combat training—as Horizons opens she is on her way to Earth's orbital platforms to avenge the murder of her brother. She is brave, clever, and honest, yet Ahni is a protagonist who remains at a distance. Ahni is often described in a manner which appears to be intended to make us admire her, rather than sympathise.
Clearly the other main characters in the book admire her, as many of them want to bind her to their plans. Although Ahni has been sent to the orbital platform for Family reasons, she is rapidly drawn into local politics. Most of the action of Horizons takes place on New York Up, a platform controlled by the North American Alliance under the auspices of the World Council. NYUp feels like a living place: it may have been engineered as a large habitat in near Earth orbit, but it has also been moulded by the needs and wants of its residents and visitors. Those manoeuvring towards self-rule are confronted by an attempt to destabilise the platform sufficiently to bring about armed intervention from Earth. The motivations of most of the players are clear, although the Administrator of NYUp seems rather inconsistent, almost simutaneously hot-headed and cool as ice. He plays a double game, appearing to serve Earth whilst supporting the leader of the moderate independence movement; despite powerful and clever enemies, no-one calls him on this until it is too late to affect his political position.
Mary Rosenblum does a neat job of gradually uncovering further levels of intrigue as the story unfolds, although some of these feel arbitrary, thrown in to move the plot along without sufficient foreshadowing. Perhaps this unevenness in the story is a result of relating offstage events too late. Rosenblum is adept at summarising with a line or two where other authors might be tempted to write in detail, but she can keep information back for too long. For example, we don't learn that there are known holes in the space defence network until someone wants to hide from it. This is a difficult balance, as too early a revelation would collapse the thriller aspects of the book, but knowledge always appears just as the protagonist needs it. Events often fall to Ahni's benefit too. With such luck alongside all her other talents, Ahni is too powerful for the threats she faces, even if she isn't consciously aware of it. As a result, any sense of peril for her slips away.
The World Council which rules humanity is also opaque. The world has survived the climate catastrophe and the Terror War, and the Council meets on a luxurious floating island, "protected by its own elite Council Security Forces ... state of the art technology and satellite protection" and "filled with the comforting hues of rose and gold and clear yellow" (p.165). It is presented as a global talking shop which also has executive power and is capable of swift decisions. Whilst it is implied that nations are represented by large delegations, some individuals seem to have disproportionate influence over key decisions. Ahni's father, "The Huang," appears to be the totally autocratic ruler of Taiwan, free to negotiate his country's position whilst also wielding the power of a business empire. He is close to a stereotype of a Chinese warlord wrapped in a business suit.
This stereotyping could well be intentional, since one of the central themes of Horizons is race. It is introduced subtly, when Ahni is described as "an unselected mix of Taiwan aboriginal, Han Chinese, and Polynesian genes" (p.13), and almost every person new to the viewpoint character is introduced similarly—"a geneselect Masai type" (p.14), "natural Mediterraneans" (p.147), "Scandinavian-euro mix" (p.212). However race and its implications are far more than "local colour," as Ahni comes to realise.
It didn't cause bloodshed in big wars, like it had once. But it was still an issue. In a global economy, with access to business partners on every continent, her father mostly did business with ... Chinese, sometimes Koreans or Cambodians. Rarely Europeans or Latinos. And he was not an exception. If anything the vanishing barriers of distance and physical isolation had increased the racial divides rather than healing them. (p.159)
Such thoughts lead Ahni to recognise the threat to the natives of the orbital platforms. They are changing rapidly under the influence of their environment. Those who have been there several generations are visibly different from the rest of humanity, to the extent that they are considered by most "downsiders" to be deformed cripples—or worse, to have been modified with non-human DNA. Such modification is the only crime in this future Earth for which the death penalty still applies.
Read for pace and style, Horizons is a good, fun book. At 300 pages, it is a brisk novel which covers a lot of ground. Rosenblum excels at writing action sequences, clearly describing events yet able to convey the sense of confusion when the viewpoint character is taken by surprise. However, Rosenblum's attempt to tackle bigger subjects can't succeed when it isn't possible to conceive that her protagonist could fail.